In the last decades in Hungary biotopes of Nanocyperion species have been reduced significantly according to the melioration and the declining of pasturing. Owing to the habitat loss more species such as the examined Lindernia procumbens, Eleocharis ovata, Centunculus minimus, Limosella aquatica, Juncus sphaerocarpus and Elatine triandra became endangered all over the country. During the researches site requirements of these species were analysed as well as their connection with the cultivated species and the soil cultivation carried out on the plough-lands. According to our experiences in West Hungary actual occurrences of Lindernia procumbens, Centunculus minimus, Juncus sphaerocarpus and Elatine triandra are related strongly to the plough-lands. Eleocharis ovata and Limosella aquatica occur on plough-lands less frequently, exist mainly on other pioneer moist habitats. It can be established in case of all the 6 examined species that their habitat spectrum has extended by the increasing in the territory of ploughs forming spacious convenient biotopes for these species. © Eugen Ulmer KG.

Which factors are the most important determinants of weed species composition in organic rice fields? Which species can be associated with the extreme values of the most important background variables? To answer these questions, we surveyed the weed flora along with 15 management and 3 environmental variables in 42 organically managed rice fields in eastern Hungary. Filamentous algae, Chara vulgaris, Chara braunii, Schoenoplectus mucronatus, Elatine triandra, and Echinochloa crus-galli were the most dominant weeds. Using a minimal adequate model containing 4 terms with significant net effects, 48.3% of the total variation in weed species data could be explained. Farm holding size (correlated with sowing type, shift crop, organic manure and water depth) was found to be the most important explanatory variable, which was followed by hand weeding, tillage type (correlated with tillage depth, shift crop and supplementary nutrients) and rice cover. Farm holding size was negatively associated with most of the aquatic plants suggesting its adverse impact on farmland biodiversity. Hand weeding appeared to be efficient against Rumex stenophyllus and Echinochloa crus-galli, but it was tolerated by Cyperus difformis. Perennial weeds like Persicaria amphibia and Bolboschoenus planiculmis were more abundant in sites without soil inversion and Lemna aequinoctialis seemed to be most tolerant for the shading effect of crop canopy. The responses of weed species to the studied variables provide new information about the assembly rules of aquatic plant communities, and our findings also can be used to optimise non-chemical weed control strategies in organic rice production.

In this compilation we present the first occurrences of 22 vascular plant species not previ ously documented from the territory of Hungary. Fifteen of the species are casuals, while seven of them are already naturalised, at least locally. We report the mass appearance and naturalization of Sagina maritima and the emergence of Carduus pycnocephalus along roadsides, single sites of Chaenorhinum litorale and Solanum elaeagnifolium near railway lines, and the localities of Lepidium latifolium and Sisymbrium volgense in various disturbed habitats, and some occurrences of Acalypha virginica in ur ban environments. The first record of Bacopa rotundifolia is from a rice field, while that of Hydrocotyle sibthorpioides is from an urban lawn, and Senna tora occurred on construction debris. Among the spe cies that appeared spontaneously as a result of earlier planting, Celastrus orbiculatus forms a natural ized population in a tree plantation, Hygrophila triflora and Pontederia cordata are present in artificial canals and lakes, and Cenchus longisetus has become naturalised and is spreading along the banks of the Danube in Szentendre. Most other species are associated with trampled or heavily disturbed habi tats in built-up areas (pavement edges, fences, ruderal areas). Alnus cordata, Eryobotria japonica, Euon ymus alatus, Paxistima canbyi, Pistacia terebinthus and Solanum pseudocapsicum are present as casuals, while Viola palmata has become naturalised in built-up environments. The naturalisation process of Allium aflatunense on a private property has also been documented.